The minimum distance from the bottom of a leaching system to the mottling layer must be what height?

The correct minimum distance from the bottom of a leaching system to the mottling layer is 18 inches. This specification is crucial in septic system design because the mottling layer, often found in soils, indicates the presence of groundwater or a higher clay content that can affect the drainage and performance of the septic system.

Maintaining this 18-inch separation distance ensures that the leach field can effectively operate without interference from the mottled soil layer, which can impede effluent movement and lead to system failure. This standard is rooted in best practices for wastewater management, as it promotes proper filtration and absorption of effluent into the soil.

The other distances mentioned do not comply with the established guidelines or could introduce risks of groundwater contamination and system inefficiency. Adhering to the 18-inch minimum is essential for the longevity and reliability of the septic system, making it an important factor in septic system planning and regulation within Connecticut.